AbstractID: 6959 Title: Dosimetry of P32 Tandem Positioning for Intravascular Brachytherapy
Intravascular brachytherapy relies on accurate delivery of dose for both treatment
efficacy and safety. For longer lesions the source may require multiple dwell positions to
adequately dose the prescribed region. This study investigated the dosimetry of a stepped
27 mm 32P catheter-based source wire.
Three types of calculations were used: analytical, experimental, and a combination
analytical-experimental method.
Our analytical technique used the MCNP4C Monte
Carlo code to calculate the spatial distribution of absorbed dose in water around the
source wire. The calculation was done for various radial distances, and at each depth the
dose distribution along the wire axis was fitted with an analytical curve. These fitted
curves were then superimposed at arbitrary step sizes and the resulting dose profiles were
graphed. Secondly, the experimental method incorporated radiochromic film attached to
a translation jig. The source wire was placed in a block of A-150 plastic with a 2.5 mm
film to source axis distance. The film was irradiated, translated with a finite step size to a
new position, and then irradiated a second time. The resulting film images were digitized
using a high resolution CCD microdensitometer.
Lastly, the combination technique
consisted of filmed wire profiles that were later translated analytically to simulate the
effects of stepping.
All three techniques confirmed our hypothesis that the optimal step size was equal to the
actual length of the radioactive source. Additionally, results established a relationship
between source overlap or gap and the resulting deviation of the dose profile. Dosevolume histogram analysis presented.
AbstractID: 6959 Title: Dosimetry of P32 Tandem Positioning for Intravascular Brachytherapy
Research is supported by Guidant Corporation